Welding Tips

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Welding Tips


Post by welder »

Found a cool site that has a bunch of info. and great video.Click on the link to see more.

[BBvideo 560,340]http://www.youtube.com/watch?v=OhqxWeAC9pI[/BBvideo]
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Your location: Kenai, AK
Location: Kenai, Alaska

Re: Welding Tips


Post by kmorin »

Hadn't seen this video before but I do note a couple of refinements needed to the adjustment of the welds shown.

First the wire speed to amperage/wattage/voltage/heat governs the arc length so there is a related rate to adjust this MIG bead. Next is the lead angle and travel speed also contribute to the final weld and last the video of the welds may not be giving me as clear an understanding of the bead as I'd have if I were looking through my own hood?

The root core of the weld is not wetted fully, ( it appears to me from 5k hours of aluminum MIG and this video) so these welds are not as well adjusted as should be the case. At the center of the seam between the two metals, there is a small area where there is no 'leading edge' of the puddle's wetted area. Beginning about 1/8" or so away from the weld puddles center of the arc, the sides of the weld are wetted and this shows by the coloration, pattern of the molten metal's lead edge and the behavior of the overall puddle as it chills behind the leading edges.

Why this matters? The center of the weld in MIG and especially in aluminum MIG is where the majority of gas is trapped in a normal bead. The presence of gas entrapment is not super critical, is common, but it does weaken the weld. So what is done to eliminate this as much as possible is to make more effort, than shown in the video, to get this center 3/16" to 1/4" arc of the puddle's lead edge to be 'wet' or to have a molten edge like the sides in the video shown.

To do this, weld modes can be used, and pulse or pulse with pulse contrary to the video's assertion will provide this wetting and it what those modes are for! Further, a wider whip or wire movement will also produce this type of improved center of weld wetting by allowing the power supply to move from short arc to spray as the puddle is whipped.

This method is what has been used by MIG welders for many years before the multi-mode, inverter vs transformer power supplies became available. By moving the arc in a wider lower case 'e' or 'c' an aluminum MIG weld can be converted from spray mode, better for wetting the lead edge into short arc, nicer for slower freeze and gassing out of the molten puddle. Also the top of a purely spray arc transfer in aluminum is not as rippled or clean looking a weld, if aesthetics are important.

This weld, shown, could be improved by # 1 increasing the wattage of the weld #2 very slightly speeding up the travel or slowing wire feed speed (same effect) #3 increasing the small step or puddle whipping motion by 2x to give more transition to the lead and trail of the puddle so the lead was thinner, and more able to heat the edges of the parent metal which also leaves a longer net weld arc time in each puddle by moving farther back and forth in each individual puddle.

Not sure if anyone is involved with the esoterica of fine tuning an aluminum MIG bead? but if you are, then the 0.045" (or larger) wire weld which flowed like 4043 (instead of the much stronger and preferred 5356 in the same alloys of parent metal) could have used a small 'tweak' to (more) fine tune the root of the final weld.

Do I think the welds will come undone? No, but if they're subject to high vibration for long periods they're more likely to fail than the same exact welds with a better arc adjustment so the core of the puddle's center along the seam of the parent materials were better fused and the weld's root face were contributing to weld strength all along the circumference instead of 80%.

IF you have the Lincoln 350MP and wish to confirm the above discussion of this weld, simply do a back break of a singled sided fillet as shown in the video. The gas entrapment of the two methods will show (drastically) what is being described.

Keyhole welds or socket welds (not discussing that type of pipe fitting) or pocket welds should always be tapered. The shoulders of the top parent metal should always be 'eased' or chamfered or the sides of the socket beveled unless there is a width to depth ration of 2:1 so the arc is no 'grounded' to the upper edges of the socket before the bottom element is fully wetted/fused/incorporated into the weld core.

Last note, ALWAYS, ALWAYS, carry a SS 'tooth brush' and scrub the weld zone just before you light up! Why this isn't shown is not clear? Again, if there is a bend break of the two welds, one cleaned prior to welding and one not cleaned, the root face entrapment and striation will make a believer of anyone who'd like to produce their best aluminum welds. Scratching the oxide layer just before welding leaves active 'furrows' in the 2-3mil oxide that allows this film to break up and blow off in the hot argon as compared to laying in a uniform unseen film when the puddle passes over the same un-abraded area. Again this is confirmed by the bend break test.

Getting under the oxide without as much cleaning is another fabulous feature of the Lincoln Pulse and Pulse with Pulse modes on this power supply, not noted in the video. Exploring the modes of this power supply takes time so, as noted, the work moved ahead without using all the 'bells and whistles' of this multi-mode MIG and TIG power supply.

This video was shot on a beautiful work table, with extremely finely cut parts, welded by an obviously experienced welder who knows good work; but the air cooled version of the the Python is a little low duty cycle for this amperage, (if you do this all day you'll have to stop and let it cool off) and the arc adjustments were a little casual in my opinion.

Kevin Morin
Kenai, AK
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